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Vision Research Jul 1996As a three-dimensional object is moving through our world, we generally obtain a vivid impression of both its structure and its motion through space. The time-course of...
As a three-dimensional object is moving through our world, we generally obtain a vivid impression of both its structure and its motion through space. The time-course of two-dimensional projections of the scene (optic flow) is important in conveying this three-dimensional information to us. The extent to which we can solve this specific inverse problem, i.e. infer a three-dimensional scene from two-dimensional flow, depends on the accuracy with which the required flow characteristics are processed by our visual system. In adequate two-dimensional processing can lead to incomplete representations of the three-dimensional world (three-dimensional metric information is lost). Then the motion and structure of objects can no longer be recovered uniquely. Consequently, metameric classes of three-dimensional representations arise (e.g. only affine properties are conserved). this study investigates under what conditions we find metameric combinations of the perceived attitude and perceived rotation of a plane. Our subjects are presented with stimuli consisting of two horizontally separated planar patches rotating back and forth in depth about vertical axes. Subjects are required to match both the attitude and the rotation magnitude of these two patches. We vary the attitude from 15 to 60 deg vertical slant, and the rotation magnitude from 28 to 98 deg. We find that the matched slant and rotation settings vary widely. For high slant values and for small rotations, attitude and rotation settings become highly correlated, suggesting metamery. For low slant values and for large rotations, the correlation almost disappears, suggesting that both quantities are estimated independently and uniquely. Our paradigm reveals that with one task and one type of stimulus a gradual transition occurs from unique settings (metric representations) to metameric classes of settings (e.g. affine representations).
Topics: Depth Perception; Form Perception; Humans; Mathematics; Models, Neurological; Motion Perception; Psychophysics; Rotation; Time Factors
PubMed: 8776486
DOI: 10.1016/0042-6989(95)00275-8 -
Cognition Aug 1998Much indirect evidence supports the hypothesis that transformations of mental images are at least in part guided by motor processes, even in the case of images of... (Clinical Trial)
Clinical Trial Randomized Controlled Trial
Much indirect evidence supports the hypothesis that transformations of mental images are at least in part guided by motor processes, even in the case of images of abstract objects rather than of body parts. For example, rotation may be guided by processes that also prime one to see results of a specific motor action. We directly test the hypothesis by means of a dual-task paradigm in which subjects perform the Cooper-Shepard mental rotation task while executing an unseen motor rotation in a given direction and at a previously-learned speed. Four results support the inference that mental rotation relies on motor processes. First, motor rotation that is compatible with mental rotation results in faster times and fewer errors in the imagery task than when the two rotations are incompatible. Second, the angle through which subjects rotate their mental images, and the angle through which they rotate a joystick handle are correlated, but only if the directions of the two rotations are compatible. Third, motor rotation modifies the classical inverted V-shaped mental rotation response time function, favoring the direction of the motor rotation; indeed, in some cases motor rotation even shifts the location of the minimum of this curve in the direction of the motor rotation. Fourth, the preceding effect is sensitive not only to the direction of the motor rotation, but also to the motor speed. A change in the speed of motor rotation can correspondingly slow down or speed up the mental rotation.
Topics: Adult; Analysis of Variance; Female; Humans; Imagery, Psychotherapy; Male; Mental Processes; Models, Neurological; Motor Skills; Psychomotor Performance; Reaction Time; Rotation; User-Computer Interface
PubMed: 9775517
DOI: 10.1016/s0010-0277(98)00032-8 -
Surgical and Radiologic Anatomy : SRA Dec 2014The objective of this study was to clarify the relationships among anatomical landmarks of the glenohumeral joint at different angles of abduction.
PURPOSE
The objective of this study was to clarify the relationships among anatomical landmarks of the glenohumeral joint at different angles of abduction.
METHODS
Fifteen volunteers (ten men, five women; mean age 29 years) were enrolled in this study. Images of externally and internally rotated positions at 45°, 90°, and 135° of abduction in the plane 30° anterior to the trunk were taken using an open magnetic resonance imaging system. Landmarks including the glenoidal long axis with its center, bicipital groove, center of the head, and humeral shaft axis were determined. Using a line set on the surface of the head in the plane parallel to the humeral axis (including the head center and bicipital groove with its parallel and perpendicular lines), the glenoid location and rotational relationships were investigated in each position.
RESULTS
The average angles of axial rotation were 48° ± 27° at 45º of abduction, 71° ± 20° at 90° of abduction, and 40° ± 27° at 135° of abduction. The trajectories of the glenoid center primarily extended over the anterior portion of the humeral head at 45° of abduction and over the posterior portion at 90° of abduction, while those at 135° of abduction were localized on a small upper portion of the head.
CONCLUSIONS
The glenohumeral relationships demonstrated that arm abduction might influence shoulder function through its effects on the portion of the humeral surface in contact with the glenoid during rotation and the resultant changes in the glenohumeral relationships.
Topics: Adult; Biomechanical Phenomena; Female; Humans; Imaging, Three-Dimensional; Magnetic Resonance Imaging; Male; Range of Motion, Articular; Rotation; Shoulder Joint; Young Adult
PubMed: 24863564
DOI: 10.1007/s00276-014-1315-5 -
Nature Communications Feb 2019Active hydrodynamic theories are a powerful tool to study the emergent ordered phases of internally driven particles such as bird flocks, bacterial suspension and their...
Active hydrodynamic theories are a powerful tool to study the emergent ordered phases of internally driven particles such as bird flocks, bacterial suspension and their artificial analogues. While theories of orientationally ordered phases are by now well established, the effect of chirality on these phases is much less studied. In this paper, we present a complete dynamical theory of orientationally ordered chiral particles in two-dimensional incompressible systems. We show that phase-coherent states of rotating chiral particles are remarkably stable in both momentum-conserved and non-conserved systems in contrast to their non-rotating counterparts. Furthermore, defect separation-which drives chaotic flows in non-rotating active fluids-is suppressed by intrinsic rotation of chiral active particles. We thus establish chirality as a source of dramatic stabilisation in active systems, which could be key in interpreting the collective behaviors of some biological tissues, cytoskeletal systems and collections of bacteria.
Topics: Algorithms; Hydrodynamics; Physical Phenomena; Rotation
PubMed: 30796222
DOI: 10.1038/s41467-019-08914-7 -
BMC Musculoskeletal Disorders May 2014Codman's paradox reveals a misunderstanding of geometry in orthopedic practice. Physicians often encounter situations that cannot be understood intuitively during...
BACKGROUND
Codman's paradox reveals a misunderstanding of geometry in orthopedic practice. Physicians often encounter situations that cannot be understood intuitively during orthopedic interventions such as corrective osteotomy. Occasionally, unexpected angular or rotational deformity occurs during surgery.This study aimed to draw the attention of orthopedic surgeons toward the concepts of orientation and rotation and demonstrate the potential for unexpected deformity after orthopedic interventions. This study focused on three situations: shoulder arthrodesis, femoral varization derotational osteotomy, and femoral derotation osteotomy.
METHODS
First, a shoulder model was generated to calculate unexpected rotational deformity to demonstrate Codman's paradox. Second, femoral varization derotational osteotomy was simulated using a cylinder model. Third, a reconstructed femoral model was used to calculate unexpected angular or rotational deformity during femoral derotation osteotomy.
RESULTS
Unexpected external rotation was found after forward elevation and abduction of the shoulder joint. In the varization and derotation model, closed-wedge osteotomy and additional derotation resulted in an unexpected extension and valgus deformity, namely, under-correction of coxa valga. After femoral derotational osteotomy, varization and extension of the distal fragment occurred, although the extension was negligible.
CONCLUSIONS
Surgeons should be aware of unexpected angular deformity after surgical procedure involving bony areas. The degree of deformity differs depending on the context of the surgical procedure. However, this study reveals that notable deformities can be expected during orthopedic procedures such as femoral varization derotational osteotomy.
Topics: Arthrodesis; Humans; Male; Models, Biological; Osteoarthritis; Osteotomy; Range of Motion, Articular; Plastic Surgery Procedures; Rotation; Shoulder Joint
PubMed: 24886469
DOI: 10.1186/1471-2474-15-175 -
PloS One 2019An intriguing simple toy, commonly known as the Notched Stick, is discussed as an example of a "vibrot", a device designed and built to yield conversion of mechanical...
An intriguing simple toy, commonly known as the Notched Stick, is discussed as an example of a "vibrot", a device designed and built to yield conversion of mechanical vibrations into a rotational motion. The toy, that can be briefly described as a propeller fixed on a stick by means of a nail and free to rotate around it, is investigated from both an experimental and a numerical point of view, under various conditions and settings, to investigate the basic working principles of the device. The conversion efficiency from vibration to rotational motion turns out to be very small, or even not detectable at all, whenever the propeller is tightly connected to the stick nail and perfectly axisymmetrical with respect to the nail axis; the small effects possibly observed can be ascribed to friction forces. In contrast, the device succeeds in converting vibrations into rotations when the propeller center of mass is not aligned with the nail axis, a condition occurring when either the nail-propeller coupling is not tight or the propeller is not completely axisymmetrical relative to the nail axis. The propeller rotation may be induced by a process of parametric resonance for purely vertical oscillations of the nail, by ordinary resonance if the nail only oscillates horizontally or, finally, by a combination of both processes when nail oscillations take place in an intermediate direction. Parametric resonance explains the onset of rotations also when the weight of the propeller is negligible. In contrast with what is commonly claimed in the literature, the possible elliptical motion of the nail, due to a composition of two harmonic motions of the same frequency imposed along orthogonal directions, seems unnecessary to determine the propeller rotation.
Topics: Computer Simulation; Engineering; Humans; Mechanics; Models, Theoretical; Motion; Play and Playthings; Rotation; Vibration; Wood
PubMed: 31242233
DOI: 10.1371/journal.pone.0218666 -
Scientific Reports Jun 2023In clinical movement biomechanics, kinematic data are often depicted as waveforms (i.e. signals), characterising the motion of articulating joints. Clinically meaningful...
In clinical movement biomechanics, kinematic data are often depicted as waveforms (i.e. signals), characterising the motion of articulating joints. Clinically meaningful interpretations of the underlying joint kinematics, however, require an objective understanding of whether two different kinematic signals actually represent two different underlying physical movement patterns of the joint or not. Previously, the accuracy of IMU-based knee joint angles was assessed using a six-degrees-of-freedom joint simulator guided by fluoroscopy-based signals. Despite implementation of sensor-to-segment corrections, observed errors were clearly indicative of cross-talk, and thus inconsistent reference frame orientations. Here, we address these limitations by exploring how minimisation of dedicated cost functions can harmonise differences in frame orientations, ultimately facilitating consistent interpretation of articulating joint kinematic signals. In this study, we present and investigate a frame orientation optimisation method (FOOM) that aligns reference frames and corrects for cross-talk errors, hence yielding a consistent interpretation of the underlying movement patterns. By executing optimised rotational sequences, thus producing angular corrections around each axis, we enable a reproducible frame definition and hence an approach for reliable comparison of kinematic data. Using this approach, root-mean-square errors between the previously collected (1) IMU-based data using functional joint axes, and (2) simulated fluoroscopy-based data relying on geometrical axes were almost entirely eliminated from an initial range of 0.7°-5.1° to a mere 0.1°-0.8°. Our results confirm that different local segment frames can yield different kinematic patterns, despite following the same rotation convention, and that appropriate alignment of reference frame orientation can successfully enable consistent kinematic interpretation.
Topics: Biomechanical Phenomena; Cross Reactions; Fluoroscopy; Knee Joint; Rotation
PubMed: 37316703
DOI: 10.1038/s41598-023-36625-z -
PLoS Biology May 2011The bacterial flagellar motor can rotate either clockwise (CW) or counterclockwise (CCW). Three flagellar proteins, FliG, FliM, and FliN, are required for rapid...
The bacterial flagellar motor can rotate either clockwise (CW) or counterclockwise (CCW). Three flagellar proteins, FliG, FliM, and FliN, are required for rapid switching between the CW and CCW directions. Switching is achieved by a conformational change in FliG induced by the binding of a chemotaxis signaling protein, phospho-CheY, to FliM and FliN. FliG consists of three domains, FliG(N), FliG(M), and FliG(C), and forms a ring on the cytoplasmic face of the MS ring of the flagellar basal body. Crystal structures have been reported for the FliG(MC) domains of Thermotoga maritima, which consist of the FliG(M) and FliG(C) domains and a helix E that connects these two domains, and full-length FliG of Aquifex aeolicus. However, the basis for the switching mechanism is based only on previously obtained genetic data and is hence rather indirect. We characterized a CW-biased mutant (fliG(ΔPAA)) of Salmonella enterica by direct observation of rotation of a single motor at high temporal and spatial resolution. We also determined the crystal structure of the FliG(MC) domains of an equivalent deletion mutant variant of T. maritima (fliG(ΔPEV)). The FliG(ΔPAA) motor produced torque at wild-type levels under a wide range of external load conditions. The wild-type motors rotated exclusively in the CCW direction under our experimental conditions, whereas the mutant motors rotated only in the CW direction. This result suggests that wild-type FliG is more stable in the CCW state than in the CW state, whereas FliG(ΔPAA) is more stable in the CW state than in the CCW state. The structure of the TM-FliG(MC)(ΔPEV) revealed that extremely CW-biased rotation was caused by a conformational change in helix E. Although the arrangement of FliG(C) relative to FliG(M) in a single molecule was different among the three crystals, a conserved FliG(M)-FliG(C) unit was observed in all three of them. We suggest that the conserved FliG(M)-FliG(C) unit is the basic functional element in the rotor ring and that the PAA deletion induces a conformational change in a hinge-loop between FliG(M) and helix E to achieve the CW state of the FliG ring. We also propose a novel model for the arrangement of FliG subunits within the motor. The model is in agreement with the previous mutational and cross-linking experiments and explains the cooperative switching mechanism of the flagellar motor.
Topics: Amino Acid Sequence; Bacterial Proteins; Crystallography, X-Ray; Flagella; Models, Genetic; Molecular Sequence Data; Phenotype; Point Mutation; Protein Stability; Protein Structure, Tertiary; Rotation; Salmonella enterica; Thermotoga maritima
PubMed: 21572987
DOI: 10.1371/journal.pbio.1000616 -
European Journal of Cell Biology Jun 2023To study processes related to weightlessness in ground-based cell biological research, a theoretically assumed microgravity environment is typically simulated using a...
To study processes related to weightlessness in ground-based cell biological research, a theoretically assumed microgravity environment is typically simulated using a clinostat - a small laboratory device that rotates cell culture vessels with the aim of averaging out the vector of gravitational forces. Here, we report that the rotational movement during fast clinorotation induces complex fluid motions in the cell culture vessel, which can trigger unintended cellular responses. Specifically, we demonstrate that suppression of myotube formation by 2D-clinorotation at 60 rpm is not an effect of the assumed microgravity but instead is a consequence of fluid motion. Therefore, cell biological results from fast clinorotation cannot be attributed to microgravity unless alternative explanations have been rigorously tested and ruled out. We consider two control experiments mandatory, i) a static, non-rotating control, and ii) a control for fluid motion. These control experiments are also highly recommended for other rotation speed settings and experimental conditions. Finally, we discuss strategies to minimize fluid motion in clinorotation experiments.
Topics: Weightlessness; Rotation; Cell Culture Techniques; Muscle Fibers, Skeletal
PubMed: 37290222
DOI: 10.1016/j.ejcb.2023.151330 -
Nature Communications Mar 2022V/A-ATPase is a motor protein that shares a common rotary catalytic mechanism with FF ATP synthase. When powered by ATP hydrolysis, the V domain rotates the central...
V/A-ATPase is a motor protein that shares a common rotary catalytic mechanism with FF ATP synthase. When powered by ATP hydrolysis, the V domain rotates the central rotor against the AB hexamer, composed of three catalytic AB dimers adopting different conformations (AB, AB, and AB). Here, we report the atomic models of 18 catalytic intermediates of the V domain of V/A-ATPase under different reaction conditions, determined by single particle cryo-EM. The models reveal that the rotor does not rotate immediately after binding of ATP to the V. Instead, three events proceed simultaneously with the 120˚ rotation of the shaft: hydrolysis of ATP in AB, zipper movement in AB by the binding ATP, and unzipper movement in AB with release of both ADP and Pi. This indicates the unidirectional rotation of V/A-ATPase by a ratchet-like mechanism owing to ATP hydrolysis in AB, rather than the power stroke model proposed previously for F-ATPase.
Topics: Adenosine Triphosphatases; Adenosine Triphosphate; Hydrolysis; Models, Molecular; Proton-Translocating ATPases; Rotation
PubMed: 35260556
DOI: 10.1038/s41467-022-28832-5